For the purpose of flexible changing settings of a network, SDN (software-defined networking) techniques have been developed. In SDN, a communication apparatus, a communication control apparatus that manages the communication apparatus, and a control network connecting the communication apparatus and the communication control apparatus are included. In SDN, the communication apparatus is specialized in a forwarding function. The communication apparatus is managed by the communication control apparatus. Hereinafter, a communication apparatus in SDN is referred to as a switch. Also, a communication control apparatus in SDN is referred to as a controller.
In SDN, network control logics for, e.g., path calculation are installed in communication control software on a controller. For example, the communication control software is software that calculates a path and notifies the controller of the path to cause the controller to set the path for switches. Hereinafter, communication control software is referred to as “application”.
One of applications in SDN is, for example, a path setting application that, upon an input of a request for setting a path between two points from a user, creates control messages for switches connecting the designated two points.
FIG. 24 is a diagram illustrating an example of a distributed-type communication control system P100. In SDN, in a case where one controller is provided, performance of the controller may fail to keep up with expansion of the scale of the network. The distributed-type communication control system P100 includes a plurality of controllers, and the plurality of controllers share management of switches (SWs in the figure) to enhance processing performance. A controller that controls a switch is referred to as a “master” for the controlled switch. For one switch, there is one controller that serves as a master therefor. Also, one controller may be a master of a plurality of switches. In FIG. 24, a controller is installed in each of a server P1 and a server P2, and the controllers included in the server P1 and the server P2 each serve as a master for three switches.
For example, because a service policy and/or a demand for band control differs depending on each organization or area of a user, a path setting application is provided for each of organizations or areas of users. In other words, in the distributed-type communication control system P100, there are plural types of path setting applications, and an instance of a same type of application operates on each of one or more servers. An instance refers to an application on a server. In the example illustrated in FIG. 24, an instance of one type of path setting application operates on the server P1 and the server P2.
FIG. 25 is a diagram illustrating an example of a flow of a control message when a path setting request is input to a path setting application in a distributed-type communication control system P100. In FIG. 25, a distributed-type communication control system P100 that is the same as that of FIG. 24 is illustrated. The example in FIG. 24 is an example of a case where a path setting request for setting a path between sites Ha-Hb is input to the path setting application on the server P1.
According to the path setting application on the server P1, a route passing through switch #1 and switch #2 is calculated as a path between the sites Ha-Hb, and a control message for setting the path between the sites Ha-Hb is created for each of switch #1 and switch #2. A master for switch #1 is the controller on the server P1. A master for switch #2 is the controller on the server P2.
Since the master for switch #1 is the controller on the server P1 on which an instance that created the control message operates, the control message for switch #1 is transmitted from the server P1 to switch #1, which is a destination. Hereinafter, a control message is simply referred to as “message”.